From cdc3321c3613911d3e91a8f7c5713461466bb47e Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Sun, 19 Dec 2021 00:28:24 +0200
Subject: [PATCH] Add an API to allow illegal inputs

---
 Core/gb.h     |  1 +
 Core/joypad.c | 17 ++++++++++++-----
 Core/joypad.h |  1 +
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/Core/gb.h b/Core/gb.h
index bcd98c4..9af5a53 100644
--- a/Core/gb.h
+++ b/Core/gb.h
@@ -657,6 +657,7 @@ struct GB_gameboy_internal_s {
         bool objects_disabled;
         bool background_disabled;
         bool joyp_accessed;
+        bool illegal_inputs_allowed;
 
         /* Timing */
         uint64_t last_sync;
diff --git a/Core/joypad.c b/Core/joypad.c
index f16aa9e..3527742 100644
--- a/Core/joypad.c
+++ b/Core/joypad.c
@@ -30,11 +30,13 @@ void GB_update_joyp(GB_gameboy_t *gb)
                 gb->io_registers[GB_IO_JOYP] |= (!gb->keys[current_player][i]) << i;
             }
             /* Forbid pressing two opposing keys, this breaks a lot of games; even if it's somewhat possible. */
-            if (!(gb->io_registers[GB_IO_JOYP] & 1)) {
-                gb->io_registers[GB_IO_JOYP] |= 2;
-            }
-            if (!(gb->io_registers[GB_IO_JOYP] & 4)) {
-                gb->io_registers[GB_IO_JOYP] |= 8;
+            if (likely(!gb->illegal_inputs_allowed)) {
+                if (!(gb->io_registers[GB_IO_JOYP] & 1)) {
+                    gb->io_registers[GB_IO_JOYP] |= 2;
+                }
+                if (!(gb->io_registers[GB_IO_JOYP] & 4)) {
+                    gb->io_registers[GB_IO_JOYP] |= 8;
+                }
             }
             break;
 
@@ -131,3 +133,8 @@ void GB_clear_joyp_accessed(GB_gameboy_t *gb)
 {
     gb->joyp_accessed = false;
 }
+
+void GB_set_allow_illegal_inputs(GB_gameboy_t *gb, bool allow)
+{
+    gb->illegal_inputs_allowed = allow;
+}
diff --git a/Core/joypad.h b/Core/joypad.h
index a360af1..21574e0 100644
--- a/Core/joypad.h
+++ b/Core/joypad.h
@@ -36,6 +36,7 @@ void GB_set_key_mask_for_player(GB_gameboy_t *gb, GB_key_mask_t mask, unsigned p
 void GB_icd_set_joyp(GB_gameboy_t *gb, uint8_t value);
 bool GB_get_joyp_accessed(GB_gameboy_t *gb);
 void GB_clear_joyp_accessed(GB_gameboy_t *gb);
+void GB_set_allow_illegal_inputs(GB_gameboy_t *gb, bool allow);
 
 
 #ifdef GB_INTERNAL